The present invention relates to a data reporting system and, more particularly, to a data reporting system which can tolerate faults on the communication channel and wherein remote stations both provide data messages to a central controller and are powered by the central controller.
In order to economically bring multiple sensor inputs to a central location, it is desirable to use a distributed time division multiplexed bus that is run throughout a building structure and is common to all of the remote stations which are providing the inputs to the bus. This type of reporting system is much more economical than the older types of systems which required a separate pair of wires between the central location and each of the remote stations providing inputs to the central location. The labor involved in running separate pairs of wires between each remote station and the central location, even more than the cost of the materials involved, makes such dedicated wire systems very expensive. By providing a single common communication channel, for example a coaxial cable, between the central location and all of the remote stations such that all of the remote stations report back over the same communication channel, labor and materials can both be economized.
However, using a single communication channel between a central location and the remote stations has the disadvantage that the opening or shorting of the wires making up the communication channel will disable all remote stations on the communication channel unless some sort of corrective action is taken. Also, the remote stations received power either from the central controller over a separate pair of wires or received power locally requiring additional wiring apparatus.